The Impact of Internal Courtyard Configuration on Thermal Performance of Long Strip Houses (2024)

1. Introduction

Climate change is profoundly connected to development and human wellbeing [1]. New analysis shows that overall greenhouse gas emissions from energy rose to their highest level ever in 2021 [2]. In particular, CO₂ emissions from energy combustion and industrial processes have grown to 36.3 gigatons (Gt), which is a 6% increase from 2020. Increased carbon emission is a significant cause of global warming, which leads to an increase in the use of mechanical air-cooling conditioning systems to provide thermal comfort, especially in hot-humid areas. The extensive use of air conditioners, in turn, brings energy consumption into a vicious circle. China is a developing country with a population of 1402.11 million [3]. The development of industry, transportation, and the urbanization process has risen rapidly in the past two decades. Energy consumption of the whole building construction is 2.147 billion tce, accounting for 47% of the total national energy consumption [4]. Accordingly, it is necessary to pay more attention to improving the thermal environment through the use of passive design strategies to reduce energy consumption.

Long strip houses (LSH), a type of narrow width and large depth dwelling, exist extensively in the hot and humid areas of southern China and other Southeast Asian countries. They are traditional vernacular buildings situated in rows for protection from typhoons and solar radiation in relatively dense neighborhoods. In China, they are also called the bamboo houses, shophouses, or arcades, which refer to “mixed-use” buildings consisting of residential and commercial functions [5]. These buildings originated in Beniapukur, India [6]. Furthermore, they can be traced back to the influx of Chinese immigrants from the densely populated southern coastal provinces of China in the 19th century until Word War II; [7]. Due to the long, usually narrow geometric shape, internal courtyards are required for natural lighting and ventilation to ensure indoor thermal comfort without relying on air-conditioning [8].

The courtyard is an intermediary space that connects outdoor and indoor spaces, representing an effort to bring in light and wind from nature. As the essential spaces of LSH, courtyards have acted on effective passive design strategies, which are available for various climatic conditions and multiple types of buildings. They are widely used in hot-humid climates. Furthermore, courtyards can create a safe and healthy environment, even during the COVID-19 period, refraining from prospective airborne diseases [9]. Nevertheless, bringing in natural wind and preventing excessive solar heat are the priority purposes for LSH to improve the thermal environment. Climate responsive design strategies of the internal courtyard can provide a relatively comfortable place for occupants. Clarifying the principles to lower air temperature and increasing the wind speed of the internal courtyard in vernacular LSH are necessary, and have withstood hundreds of years and been crafted over generations to incorporate passive design parameters in response to local climate conditions [10]. Moreover, the passive design principles of the courtyard are more critical in the transformation and application of LSH.

Despite houses having courtyards for thousands of years in the long history of architecture in China [11], it has been taken for granted and ignored in the last couple of centuries. Currently, at the pace of modern housing development in different countries with various climates, more attention has been given to the concept of solving complex problems in dense cities. However, only a few designers have looked beyond the aesthetic characteristics in contemporary housing development, subtly addressing the environmental impact of the courtyard as a passive strategy to improve thermal comfort, energy-saving efficiency, and sustainability. Moreover, some guidelines about courtyard design are not clear and definite to designers.

An earlier and serious discussion on analyzing the thermal performance of the courtyard was conducted by Dunham, and it showed that the open courtyard building exhibits a better energy performance in hot-dry and hot-humid climates [12]. Subsequently, the thermal performance and air flow of courtyards was evaluated through the simulation method [13,14,15,16]. Likewise, the courtyard as a passive cooling strategy was illustrated through field measurement in Malaysia [17,18,19], Iran [20], etc. Recent studies about strategies for improving the courtyard thermal comfort have been proved useful in various climates (e.g., the use of water, sprays [21], greeneries, and landscape elements [22], the incorporation of larger surface area, high thermal mass, shallow plan form, narrow spaces for shade [23], the addition of trees or galleries [24] (hot-arid climate), the use of soil, grass [25], water pool, and urban greeneries plus decreasing the albedo of facades [26] (temperate climate), use of trees, grass, strategic building design modifications [27], increasing the height and definite long axis of orientation [28], and decreasing the albedo of wall enclosures [29] (hot-humid climate)). The effect of parameters was also evaluated concerning the aspect of geometric proportions and space placement [30], dimensions, and orientation as the most influential design variants to provide appropriate thermal comfort in the courtyards [31]. However, most of the work carried out on the courtyard lacks clarity regarding the configuration of the courtyard to improve indoor thermal comfort during a typical hot day, especially in LSH, the particular type of houses in dense cities.

Previous studies focused on the courtyard thermal performance of LSH with courtyards in hot-humid climates, which provided basis for this research. The survey by Tetsu Kubota revealed that the small courtyards were effective in enhancing night ventilation and nocturnal radiant cooling in the high mass shophouses [32]; space volume, openness, and courtyard height were the significant components affecting the air temperature and RH profiles [33]. Wang Han classified shophouses into types of serial, partitioned, and combined types in Southeast Asian port cities [34]. Yin Shi focused on the mechanism of LSH streets on outdoor thermal comfort by researching the contribution of scale on the microclimate of shophouse streets via simulation software (ENVI-Met) [35,36]. As shown in Figure 1, configurations of the internal courtyard are different in the practical house design, but what are the effects of courtyards on thermal performance that have impacts on human comfort? What are the design principles of internal courtyards when designing buildings in hot-humid climates? There is still a paucity of studies to identify predictors of internal courtyard configurations on the thermal performance of LSH in hot-humid areas.

This paper mainly focuses on the internal courtyard configuration design parameters which influence the LSH indoor thermal environment. It presents an in-depth study on how the internal courtyard affects the indoor thermal and ventilation of natural-ventilated LSH in the hot-humid climate of Hainan Island. Therefore, according to the progressive relationship, three research steps are formed as follows:

A comprehensive literature review is carried out on passive cooling design strategies, courtyard, thermal performance, and comfort in hot-humid areas. Climate conditions are analyzed, along with a typical city selection for design recommendations, based on the Mahoney table.
Field investigation is conducted on six traditional LSH research cases, which are located in different cities on Hainan Island. Detailed building information, including location, story, top opening, courtyard profile shape, and ratio of height to depth (H/D), are clarified, and the statistics lay the foundation for the simulation.
Simulation models based on the prototype of LSH are built according to three internal courtyard configuration elements—top opening, sectional shape (I, L, staggered, expanded, and contracted shape), and the ratio of H/D—which are based on field investigation. The ventilation and temperature distribution under different simulation conditions are analyzed and discussed.

In brief, the above comprehensive research is carried out by combining qualitative and quantitative studies. The innovative contribution of this paper is proposing a correlation between internal courtyard configuration on the indoor and outdoor thermal performance of LSH in hot-humid climates in China. A clarification on the relationship between courtyard form and its thermal environment is important for both practical projects and modern LSH design methodology, which plays a vital role in formulating design guidelines for architects designing these types of buildings.

2. Methodology

Different combinations of natural conditions and internal courtyard configurations cause different thermal environments of indoor spaces, which affect people’s daily activities and building energy consumption. In order to determine the role of the internal courtyard in building thermal performance, indoor environment and passive design strategies need to be evaluated. With the data on thermal performances of different cases, the courtyard configuration can be optimized for the research objective of improving the building’s thermal environment.

As shown in Figure 2, methods and materials are adopted with three combinations, namely (1) climate analysis using the Mahoney table for passive design strategies, (2) field investigation of six typical LSH, and (3) computational fluid dynamic (CFD) simulations for the thermal environment. The three methods are interrelated with research contents to achieve the design principles of internal courtyard of LSH.

The proposed methodology starts with the analysis of climate data from the site of Hainan Island. The local climate was associated with appropriate strategies in terms of bioclimatic design by using the Mahoney table [41]. The Mahoney table methodology is a set of reference tables that classifies climate data, e.g., air temperature, relative humidity and precipitation, and gives recommendations for the climate-appropriate design of buildings [42]. The analysis of location and site, which can comprehensively describe the distribution of LSH in Hainan Island, creates the foundation for investigating local houses with courtyards.

A field survey, aiming to show spatial characteristics of the internal courtyard, was promoted in different districts of Hainan Island. The field investigation contained content of on-site observations, photographic recording, drawing, and building visual models. Six folk houses with internal courtyards were selected for field investigation, which are representative buildings of LSH.

Computational fluid dynamic (CFD) simulations significantly improve the efficiency of assessing the microclimate and the performance of design schemes, which makes microclimate analysis more efficient and provides architects and researchers the time to complete other design arrangements [43]. The building simulation of thermal environment distribution in this study is carried out using Autodesk CFD software, which can conduct simulation analysis of air flow, heat conduction, and convective heat. By setting boundary conditions, it can obtain the vector distribution of indoor and outdoor air temperature (T_a), mean radiant temperature (MRT), and wind speed (V_a) of the building, form visual 2D and 3D images and videos, and obtain specific values of relevant parameters of the thermal environment through point distribution.

The quantitative evaluation is based on the previous climate analysis and case investigation. Based on the local buildings, the simulation model is a long strip brick house with an internal courtyard, 21 m in length and 4 m in width. The changes of courtyard configuration in simulation models are based on three parameters: top opening mode, the shape of courtyard, and the ratio of height to width (H/D).

The local latitude and longitude are set as 20°2′ N and 110°33′ E, respectively, according to the location of Haikou, China. The outdoor climate data of calculation parameters, under natural ventilation conditions in summer, was chosen for simulated operation by searching the standard [44]. In detail, the T_a, RH, and V_a are set at 32.2 °C, 68%, and 2.7 m/s (S), respectively, as shown in Table 1. Thermal comfort factors, including metabolic rate and clothing thermal resistance, are set as 1.0 met and 0.5 clo. Looking into the climate data of Haikou in summer, the solar loads are selected the day of July 26 at 12:00 GMT +8 time zone, which is an average hot and sunny day. The volume of the grid size is 500 times more than the model size to ensure the accuracy of flow field simulation. The adaptive predicted mean vote (APMV) is adopted as the indoor thermal environment evaluation [45] for the simulation results comparison. The lower the value of APMV, the better the indoor thermal environment.

3. Results and Discussion

3.1. Site and Climate Analysis

Hainan is a low latitude district in southern China. LSH in Hainan Island is divided into two different types, north and south, in terms of function and geographical distribution [46]. The north is mostly a combination of the first floor of a sales store along the street and 2 or 3 stories of residence, which are mainly concentrated in Haikou, Wenchang, Danzhou, and Qionghai cities (see Figure 3). Most of these buildings have adopted internal courtyards for natural lighting and ventilation. The south is mainly for living, and the depth scale is not as long as the previous one. They spread in towns and villages in Sanya, Ledong, and Lingshui. As the depth is not that long, there is generally no inner courtyard. Consequently, the field survey mainly focuses on the LSH with internal courtyards in dense cities, located on the north of Hainan Island. The climate data of Haikou, a city with LSH, is selected as representative climatic information.

Mahoney table methodology is proposed by Koenigsberger in the research of tropical areas [47]. It is formed by collecting climate data, including temperature, relative humidity, and precipitation (see Figure 4). Design recommendations for each month can be obtained according to the Mahoney table. The shade represents appropriate design guidelines (see Table 2).

The table shows that air movement is essential from April to October, seven months, and desirable for two months, which occupies most of the year. Protection against heavy rain is needed from June to October, while thermal capacity is not considered for the whole year. According to the Mahoney table, buildings in this climate recommend a north-south orientation, lightweight internal and external walls and roofs, and an opening of medium size. The space can be relatively open and protected from cold wind only in January. Rooms arranged on one side, with permanent provision for air movement, are recommended. This indicates that shading is essential to buffer against intense solar radiation, and ventilation is necessary for protection from heat. In short, cooling strategies and heating protection are considered the priority in this area.

3.2. Results of Field Investigation

Six representative vernacular dwellings were selected for field survey based on the site analysis in Section 3.1 (see Figure 3), which were all LSH with an internal courtyard on Hainan Island. All of them are selected according to the records of arcades in the literature [48], which basically cover the location and different type of every existing arcade block in Hainan Island. The architectural details are shown in Figure 5 and Table 3. Most of them have been built for nearly one hundred years. A study on the investigation of residential cases is conducive to preparing for the establishment of simulation models.

3.2.1. Architectural Layout and Form

Considering the frequent typhoons in summer and the short width of LSH, they are connected with adjacent houses and built in the form of groups along the street. Since the direction of the street is not determinate, the orientation of the buildings vary. Consequently, the courtyards in the LSH play an important role in natural lighting and ventilation. Generally, there is only one courtyard in the building when the depth is less than 20 m. As the length of the building increases, the number of courtyards grow. When the depth exceeds 40 m, buildings have two or three courtyards, or even more.

3.2.2. Function Deployment

The LSH is called an arcade, shophouse, or bamboo house, which is a particular type of traditional building in the south of China. The majority of these buildings are two or three stories, rarely more than four floors. As mentioned in Section 3.1, most of these buildings with internal courtyards are used for commercial sales and living. Specifically, the plane is divided into three parts: front, middle, and back. The front is the part of commercial activities along the street, including the overhanging veranda forming a semi-open space and open halls to accommodate shopping space; the middle is the traffic connection part, containing courtyard, stairs, and aisles; the back is the living and storage part, comprising dining room, kitchen, warehouse, etc.

3.2.3. Spatial Size and Scale

The width of LSH is approximately 3–6 m, and the length is generally between 15–50 m. The ratio of H/D is 1:5–1:8, and some are even more than 1:12 (see house E in Figure 5). Under the intensive solar radiation considerations of Hainan Island, the large area of external walls in the length direction are shared by adjacent buildings, which can effectively reduce solar radiation and minimize the indoor thermal temperature.

The plane of the courtyard is square or rectangle, and very few are irregular. The height of the courtyard depends on the wall interface around the yard. According to the profile analysis, the size of height is larger than that of the depth in the interior courtyard. The ratio of H/D ranges from 1.5:1 to 5:1, except for the backyard C2 of house C. The sectional shape of the courtyard is mainly rectangular, which is a straight tube in I shape. A few of them are L-shaped due to the platforms or overhangs. With the development of techniques and diversified demand for architectural spaces, different shapes of courtyard sections have appeared in modern LSH in hot and humid areas, which should be considered in the further study of courtyard design. Therefore, in order to show the diversification of the internal courtyard’s sectional shape and support the simulation conditions in “Section 3.3.2”, expanded, contracted, and staggered shapes were added, as shown in Figure 1, in addition to I shape and L shape.

3.2.4. Construction and Materials

The exterior walls of the buildings were mostly built with bricks. Later, with the emergence of concrete, the buildings adopted reinforced concrete structures. The indoor space is partitioned with wooden boards to utilize the air circulation on the upper side. In general, materials used in the building include bricks, steel bars, cement, glass, wood, etc. There are three types of roofs: sloping roof, flat roof, and flat-slope combined roof. The roof construction method is the same as other traditional houses on Hainan Island [49]. Most of the windows are wooden casem*nt windows, while some are grille or shutters.

3.3. Building Thermal Performance of Simulation

3.3.1. Top Opening

The model is 4 m wide and 21 m long. The front and back rooms are of the same size. The building is an LSH with a pitched roof on the northern and southern sides, and a flat roof on the inner side close to the courtyard. The central inner courtyard is 7.5 m high and 3 m deep. Two different openings form at the top of the courtyard, open and semi-open, which are simulated to investigate thermal environment changes in the buildings with an internal courtyard (Table 4). It is evident in Figure 6 that there is little difference in the wind environment between the two conditions. The average V_a of indoor rooms and courtyard in Model 1 is slightly higher than that of Model 2, yet the difference is negligible.

The difference is more evident in the thermal environment distribution. As Figure 7 shows, the T_a of the back room and courtyard in Model 2 is significantly higher than in the other one. Specifically, the average T_a of the courtyard in Model 1 is 3.0 °C and 1.0 °C lower than that of Model 2 on the first and second floor, respectively. Meanwhile, the average T_a of the back room on the first and second floor in Model 2 is 1.7 °C and 0.5 °C higher respectively than that of Model 1. The results indicate that the top opening, shaded or not, has less influence on the wind, and thermal environment of front room (the room in the same direction as the wind); however, it plays a vital role in the thermal environment of the back room and courtyard.

The adaptive predicted mean vote (APMV) is calculated on the basis of simulation results and physical quantity. Figure 8 shows that, similar to the law of T_a changes, the APMV of the back room and courtyard vary more than the front room, which is higher in Model 2. The results illustrate that the building with a covered top yard, leaving a ventilation gap, takes advantage of the indoor and outdoor thermal regulation, which can effectively reduce the direct solar radiation from the top and take into account natural ventilation. In the design of practical projects, a covered roof on the top of the internal courtyard can be put into practice, keeping a connection with the outdoors through the opening, which makes full use of heat and wind pressure for heat dissipation.

3.3.2. Sectional Shape

The width and length of these models is still the same as the one in Section 3.3.1, while the shape of courtyards have changed for different types. The width of courtyards is the same. The depth of the narrowest part of the L-shaped internal courtyard is 3 m, and the depth of the widest part is 6 m, the depth of the widest part of the expand and contract shaped yard is 9 m, and the upper and lower depths of the staggered yard are 6 m. According to the different shapes of the internal courtyard section, the simulation models are divided into four groups (Table 5): I shape, L shape, expanded and contracted shape, and staggered shape.

In the L shape group, there are four different configuration types: back terrace (Model 3), back cornice (Model 4), front terrace (Model 5), and front cornice (Model 6). When comparing the average V_a of the four models, the courtyard and front room of Model 5 has relatively good wind conditions. However, the back room wind environment of Model 5 is extraordinarily poor. As Figure 9 shows, a change in the rear side of the courtyard section is conducive to the ventilation of back rooms, but takes disadvantages of back rooms for thermal environment (Figure 10). The results of APMV values indicate that the terrace design approach is detrimental to the thermal comfort of indoor and outdoor spaces, especially on the second floor. When comparing the APMV of four types of L shape courtyard sections, the front and back rooms of Model 4 has a better thermal environment, which is similar to that of the Model 2 (I shape).

Judging from the change of profile shape, the courtyard space of Model 7 and Model 8 expanded and contracted from bottom to top, respectively. Figure 9 and Figure 10 show that the cross ventilation changes little between the two types compared to air temperature changes. In particular, the average V_a of courtyard on the second floor of Model 8, only decreases by 0.12 m/s, but the T_a drops by approximately 3.0 °C. Consequently, the APMV value reduces as the courtyard adopts a contracted shape. In the front room on the first floor of Model 8, the APMV has dropped below 1, which is the only one evaluated as level II; (−1 ≤ APMV < −0.5, or 0.5 < APMV ≤ 1) in the assessment level of the non-artificial thermal environment of all rooms.

In group four, the top forward and bottom forward of courtyard sectional staggered shapes in Models 9 and 10 are put forward for simulation. The wind shadow area formed on the north side of Model 10 is larger than the other one. For the natural ventilation of indoor and outdoor spaces on the second floor, Model 10 is significantly better than Model 9, while the result is contrary to that on the first floor. The results indicate that when the staggered courtyard shape is adopted in the design, the top forward type should increase the window-to-ground ratio on the second floor to improve the wind environment. Similarly, it also applies to the bottom forward type on the first floor. For the thermal environment, T_a in the back room of Model 10 is significantly higher than that of Model 9, both on the first and second floors. Therefore, the APMV of Model 10 is higher than Model 9, which suggests that the top forward staggered type can bring about a relatively good thermal adaptive environment (see Figure 11).

Compared to the previous relatively better model with four different shapes of models, Models 2, 4, 8, and 9, the courtyard sectional shape of contracted (Model 8) can create the best thermal environment. The second is the I shape of the courtyard section, which is Model 2.

3.3.3. Ratio of H/D

Three different ratios of height to the depth of internal courtyards are simulated to investigate how the enclosure dimension changes of courtyard effect on the thermal environment. The whole building’s length, width, location, and floor height are determined as a determinate parameter, while courtyard proportion varies according to the number of floors and the depth of the courtyard. The width of the courtyard is still 3.6 m. The height and depth of these three models are shown in Table 6. Hence, three different models are developed by the ratios 2.5:1 (Model 2), 1:1 (Model 11), and 5:1 (Model 12).

It is evident in Figure 12 that, as the depth of the courtyard of Model 11 adds up to 2.5 times that of Model 2, the average V_a of the courtyard is reduced by half. The indoor room distribution V_a changes is not as significant as changes of T_a. Figure 13 shows that the back rooms, both on the first floor and second floor, are 2–3 °C higher than that of Model 2. Similarly, the T_a of the courtyard with the lowest ratio (Model 11) has risen on the first floor compared to Model 2, and, likewise, the APMV. Overall, it is inferred that by increasing the depth, it is easier for solar radiation to enter the internal courtyard. As a result, the back room is limited to form a cooler thermal environment.

Looking at the height changes of the internal courtyard, Model 12 is twice as high as Model 2. It was found that the ventilation and thermal environment can get better on the first and second floor of indoor spaces. Especially for the back room, thermal environment optimization is more apparent compared to the front room, as Figure 13 shows. To be precise, the average T_a of back rooms on the first and second floors decreased by 1.2 °C and 1.3 °C, respectively. Consequently, The APMV value of the rooms on the lower two floors get smaller, along with the decrease of T_a. However, as Figure 14 shows, T_a and APMV of the rooms on the top two floors in Model 12 is higher than that of Model 2. The results suggest that, with the raised height of the courtyard and the increased number of stories, the thermal environment for heat insulation of lower spaces can get better because of the upper rooms [50]. In a courtyard with higher wall enclosures (4 stories) and a ratio of H/D (5:1), a lower value of APMV can be obtained on the lower floors; however, for the top floor, it is challenging to acquire thermal comfort without consideration of roof insulation.

Through the above three simulations, the internal courtyard configuration design guidelines of LSH are formed, as shown in Table 7.

4. Conclusions

Courtyards play an essential role in enhancing natural ventilation and promoting building heat dissipation. The rational design of courtyards can improve the thermal comfort of indoor and outdoor spaces. Scientific studies have focused on the principle of courtyards regulating micro-climate. Nevertheless, the configuration of courtyards, for instance, the size, shape, scale, and proportion, is significant in the building design. Accordingly, the impact of internal courtyard configuration of LSH in the hot-humid areas of China is studied in this paper. According to the field investigation and simulations, the key findings are summarized in the following points:

Internal courtyards have widely existed in the LSH in Hainan Island, which is a typical hot-humid area. The number of courtyards depends on the depth of the building. The larger the depth, the more courtyards.
Courtyards covered by semi-open roofs take advantage of indoor and outdoor ventilation and thermal regulation, which can directly prevent solar radiation and heat from the top and take into account air movement.
Courtyard sectional contracted shape, which is upper narrow and lower width, is more conducive to creating a good indoor and outdoor thermal environment compared to other shapes; the back cornice of the L shape has a relatively good thermal environment in the front and back rooms, which is similar to that of the I shape. When adopting a staggered courtyard, it is better to choose a top forward staggered form.
As the height of the courtyard increases, it is beneficial to reduce the air temperature of lower indoor and outdoor spaces. The ratio of H/D should not be less than 1 when an embedded courtyard is designed in the building. An excessive small proportion of H/D is more likely to receive direct solar radiation in the back rooms.

Based on the study, the thermal adjustment of internal courtyards is clarified, and three design parameters of courtyard design are determined in the LSH, under the premise of fulfilling the requirements in hot-humid areas. The limits of the simulation software used is as follows: the simulation time was fixed and identical, but not for a whole day or an even longer time. Future studies will focus on the energy consumption of buildings with courtyards, based on exploring the variety of courtyard configurations and examining the effectiveness for further improving indoor thermal performance characteristics through practical projects. Internal courtyard design guidelines, which can serve as practical references for architects in building designs, will be drawn up in the hot-humid areas of China.

Author Contributions

Conceptualization, Q.S.; methodology, Q.S.; software, Q.S. and Z.L.; validation, Q.S., Z.L. and L.B.; formal analysis, Q.S.; investigation, Q.S.; resources, Z.L.; data curation, L.B.; writing—original draft preparation, Q.S.; writing—review and editing, Q.S.; supervision, Z.L.; funding acquisition, Q.S. and Z.L. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China, 51590913 and the Social Science Foundation of Shaanxi Province, 2022J052.

Data Availability Statement

Data is contained within the article or non-published material.

Acknowledgments

This research was supported by Hainan Provincial Department of Housing and Urban-Rural Development.

Conflicts of Interest

The authors declare no conflict of interest.

Nomenclature

H/D	Height to depth
LSH	Long strip houses
CFD	Computational Fluid Dynamics
APMV	Adaptive predicted mean vote
T_a	Air temperature
RH	Relative humidity
MRT	Mean radiant temperature
V_a	Wind velocity

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Figure 1.Different sectional shapes of courtyards in modern LSH in Vietnam: (a) VOM House [37]; (b) Gardening terrace house [38]; (c) A house in trees [39]; (d) Tropical Cave House [40]. (From left to right).

Figure 2.Research method framework.

Figure 3.LSH distribution in Hainan Island.

Figure 4.Climatic data in Haikou.

Figure 5.Representative selected vernacular houses.

Figure 6.Simulated spatial distributions of V_a in Models 1–2 at 12:00 at 1.2 m height on each floor.

Figure 7.Simulated spatial distributions of T_a in Models 1–2 at 12:00 at 1.2 m height on each floor.

Figure 8.APMV values in Models 1–2 at 12:00 at 1.2 m height on each floor.

Figure 9.Simulated spatial distributions of V_a in Models 2–10 at 12:00 at 1.2 m height on each floor.

Figure 10.Simulated spatial distributions of T_a in Models 2–10 at 12:00 at 1.2 m height on each floor.

Figure 11.APMV values in Models 2–10 at 12:00 at 1.2 m height on each floor.

Figure 12.Simulated spatial distributions of V_a in Models 2, 11, and 12 at 12:00 at 1.2 m height on each floor.

Figure 13.Simulated spatial distributions of T_a in Models 2, 11, and 12 at 12:00 at 1.2 m height on each floor.

Figure 14.APMV values in Models 2, 11, and 12 at 12:00 at 1.2 m height on each floor.

Table 1.Simulation boundary conditions.

Simulations Input Parameters
Location		Haikou, China (20°2′ N and 110°33′ E)
Turbulence model		K-ε
Building data	Model size	V_m = d × w × h
	Grid size	V_d = 8 d × 5 w × 5 h = 200 V_m
	Model material	Brick
	Windows	Open
	Thermal conductivity	[W m⁻¹ K ⁻¹]	0.4
Thermal comfort factor	Metabolic rate	[met]	1.0
Thermal comfort factor	Clothing thermal resistance	[clo]	0.5
Meteorological data	Outdoor temperature	[℃]	32.2
Meteorological data	Relative humidity	[%]	68
Inflow boundary	Wind direction		S
Inflow boundary	Wind speed	[m s⁻¹]	2.7
Outflow boundary	Wind pressure	[pa]	0

Table 2.Design recommendations for each month of Haikou based on Mahoney table.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Total
H1: Air movement essential													7
H2: Air movement desirable													2
H3: Rain protection necessary													5
A1: Thermal capacity													0
A2: Outdoor sleeping													0
A3: Protection from cold													1

Table 3.General information about the internal courtyard of houses in filed survey.

Code	Location	Storey	Court Yard	Top Opening	Courtyard Profile Shape	Courtyard Size (m)			Ratio of H/D
Code	Location	Storey	Court Yard	Top Opening	Courtyard Profile Shape	Width	Depth	Height	Ratio of H/D
House A	Shengli street, Wenchang	2	C1	Open	Square	2.1	2.1	4.2	2:1
House A	Shengli street, Wenchang	2	C2	Open	Rectangle	4.0	0.8	4.0	5:1
House B	Xinying, Danzhou	2	C	Semi-open	Rectangle	1.5	2.2	6.6	3:1
House C	Nanfeng town, Danzhou	2	C1	Closed	Rectangle	1.8	1.4	3.5	2.5:1
House C	Nanfeng town, Danzhou	2	C2	Open	Rectangle	6.2	7.2	2.6	1:3
House D	Baiyanxu, Wenchang	3	C	Open	Rectangle	3.0	2.1	8.4	4:1
	Zhongshan road, Haikou		C1	Open	Square	2.7	2.7	5.4	2:1
House E		3	C2	Open	L shape	4.8	2.6	7.8	3:1
			C3	Open	Irregular	4.8	7.5	5.0	1.5:1
House F	Xinhua road, Haikou	2	C	Open	Rectangle	1.2	2.5	8.0	3.2:1

Table 4.Different top openings of the courtyard.

Code	Model 1	Model 2
Sectional Perspective
Top opening	Semi-open/shaded	Open/unshaded

Table 5.Different sectional shapes of the courtyard.

Code	Model 2	Model 3	Model 4	Model 5	Model 6	Model 7	Model 8	Model 9	Model 10
Section
Shape	I	L				Expanded & Contracted		Staggered

Table 6.Different sectional shape of the courtyard.

Code	Model 2	Model 11	Model 12
Sectional perspective
Height	7.5 m	7.5 m	15.0 m
Depth	3.0 m	7.5 m	3.0 m
Ratio of H/D	2.5:1	1:1	5:1

Table 7.Internal courtyard configuration design guidelines of LSH.

Parameter	Configuration	Design Guidelines
Number	Larger depth, number of courtyard increase	Internal courtyards have widely existed in the LSH in Hainan Island, which is a typical hot-humid area. The number of courtyards depends on the depth of the building; the larger the depth, the more courtyards.
Top opening	Semi-open /shaded	Courtyards covered by semi-open roofs take advantage of indoor and outdoor ventilation and thermal regulation, which can block the heat direct solar radiation from the top and take into account air movement.
Sectional shape	Narrow upper and wide lower/upward contracted	Courtyard sectional contracted shape, which is upper narrow and lower width, is more conducive to creating a good indoor and outdoor thermal environment compared to other shapes.
	Top sunshade	If it is necessary to adopt the form of expanded/funnel shaped courtyard, shading measures (such as louvers and grilles) should be taken into consideration on the top space, which is to ensure the air flow and thermal radiation shielding.
	Staggered	When adopting a staggered courtyard, it is better to choose top forward staggered form, which can bring in the natural wind into the courtyard and promote the ventilation of indoor space in the LSH.
Ratio of H/D	Greater than 1	The ratio of H/D should not be less than 1 when an embedded courtyard is designed in the building. Excessive small proportion of H/D is more likely to receive so much direct solar radiation that causes discomfort in the back rooms.
Ratio of H/D	Height/floors increase	As the height/floors of courtyard increases, it is beneficial to reduce the air temperature of lower indoor and outdoor spaces. The thermal environment of lower spaces can get better because of the upper rooms for heat insulation.

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